Impact behaviour of auxetic Kevlar®/ epoxy composites

Experimental study was performed to investigate fracture and impact properties of novel Auxetic Kevlar^® laminated composites. For comparison, standard Kevlar^® woven composites with and without polyurethane surface treatment were also considered in this study. For these three composites, short nylon fibers of two different fiber lengths and three different fiber densities were flocked between laminates. Vacuum infusion process along with optimized compaction was employed to fabricate composites. The double cantilever beam configuration was used to investigate the fracture properties. The Auxetic Kevlar^® composites showed a significant improvement of 225% in fracture toughness compared to regular woven Kevlar^® composites. Furthermore, the initiation toughness was increased by 577% with the application of flocking in Auxetic Kevlar^®. During impact testing, the Auxetic Kevlar^® reinforced composites showed a significant reduction in damaged area compared to woven counterpart. On the other hand, the reduction in damaged area influenced the reduction in impact energy absorption. (paper)